Fac-simile of Holmes-map of the province of Pennsylvania : with the names of the original purchasers from William Penn, begun in 1681.
Shows rural landholders' names and lots in the Philadelphia region.
Alternate title at top: A map of the improved part of the province of Pennsylvania in America : begun by William Penn, proprietor and governor thereof, anno 1681.
Facsim. "Reproduced from the original in the Philadelphia Library by the anastatic process."
Original version: A map of the province of Pennsilvania : containing the three countyes of Chester, Philadelphia, and Bucks as far as yet surveyed ... by way of townships / by Tho. Holme, survey'r gen'l. London : Sold by Rob. Greene ... and by John Thornton, [1687?].
Includes inset of "The city of Philadelphia," statement of dedication "By John Thornton & Robert Greene," and coat-of-arms.
Ristow. American maps and mapmakers
LC copy sectioned, laminated, and mounted on cloth backing.
Available also through the Library of Congress Web site as a raster image.
In the 17th century, maps took a huge leap forward. Mathematical and astronomical knowledge necessary to make accurate measurements had evolved. English mathematicians had perfected triangulation: navigation and surveying by right-angled triangles. Triangulation allowed navigators to set accurate courses and produced accurate land surveys. Seamen learned to correct their compasses for declination and had determined the existence of annual compass variation. Latitude determination was greatly improved with the John Davis quadrant. The measurement of distance sailed at sea was improved by another English invention, the common log. Longitudinal distance between Europe and Québec was determined by solar and lunar eclipses by the Jesuit Bressani in the 1640s and by Jean Deshayes in 1686. With accurate surveys in Europe, the grid of the modern map began to take shape.